in

in the classroom是在教室内（比如说丽莉正在教室里看书：Lily is reading in the classroom.），很少用in classroom（在教室里），更常用的是in class，指的是上课（比如说我们正在上课：We are in class.）

in the classroom例句

She was alone in the classroom.

她独自一人在教室里。

Maybe he is in the classroom.

他可能在教室里。

Teachers will never be replaced by computers in the classroom.

课堂上电脑永远不会取代老师。

There was complete anarchy in the classroom when their usual teacher was away.

任课老师不在时，班上一片混乱。

Discipline in the classroom is very slack.

班里纪律十分松懈。